With typical coin operated public telephones a caller manually dials appropriate information over transmission means, such as local wire loops connected to a computing and switching means called a “central office switch,” which first collects the dialed caller information, processes the call, and controls the switching, accessing, and routing of caller information over long-distance transmission means to other similarly-arranged computing and switching means that are remotely located. In the past voice telephone calls were connected to a human operator to provide assistance in accounting and billing for a call. Access over additional long-distance transmission means was provided to a last computing and switching means connected to the local loop of a destination telephone terminal instrument and various computing and switching means which record the call numbers and timing and further arrange the accounting and billing for the public telephones and calls.
U.S. Pat. No. 4,935,956, Hellwarth, et al. describes a public phone service that permits and arranges long distance calls, the charges of which can be billed to either a credit account, the called party, or to a third party with a computer recording and accounting for the revenues collected from the telephone service. This is an example of a controlled public telephone system.
Telephone instruments which are accessible to the public for placing telephone calls are used in locations which are accessible to persons who are not necessarily responsible for their use. Often, public telephones are located in areas where restrictions must be placed on their use. For example, in prisons limitations are placed on the destination telephones which may be called. In order to control the destination numbers it is necessary to detect attempted three-way calls. U.S. Pat. No. 5,768,355, Salibrici et al., shows a three-way call detection system which uses digital signal processing to identify a third party connection. The three-way call detection of this patent is used in the Commander™ telephone system supplied by Science Dynamics Corporation. This is another example of a controlled public telephone system.
Recently, voice over internet protocol (VoIP) has been used for transmitting packets of data representing voice telephone messages. A VoIP gateway permits VoIP sessions to be conducted with called parties such as a called party having a PC connected to a Public Switching Transmission Network (PSTN) by a telephone line.
It is an object of the present invention to use Voice over Internet Protocol networks to transmit information from a controlled public telephone system.